The present invention relates to a continuous process for making zippered plastic bags and particularly to the method of installing a plastic slider on the plastic zipper profile attached to the mouth of the bag.
Plastic reclosable fasteners or zippers with sliders are well known in the art. The plastic zippers have profiles and include a pair of male and female fastener elements in the form of reclosable interlocking rib and groove elements with a slider riding on the zipper for opening and closing the rib and groove elements. Sliders are generally of a U-shaped configuration having inwardly extending shoulders at the open end of the U to maintain the slider on the zipper as the slider is moved from one end to the other of the zipper. In the manufacture of thermoplastic film bags, a pair of the male and female fasteners extend along the mouth of the bags and these male and female elements are adapted to be secured in any suitable manner to the flexible walls of the thermoplastic film bags. These elements may be integral marginal portions of such walls or they may be extruded separately and thereafter attached to the walls along the mouth of the bag.
For reasons of economy, it is desirable to make the zippered plastic bags by a continuous bag making process. In such process a continuous web of plastic bag material having a plastic zipper profile attached to one edge thereof is moved along a predetermined path. The movement of the zipper and web bag material is periodically interrupted to assemble the slider with the zipper by a relative transverse maneuver and to concurrently form a side seal across the thermoplastic sheets between adjacent bags and to sever the completed bag from the end of the continuous web of plastic bag material. At the same time end stops at the ends of the zipper may be formed to prevent the slider from going off past the end of the zipper and coming off of the bag. Examples of this are disclosed in Herrington et al U.S. Pat. No. 5,131,121 and U.S. Pat. No. 5,161,286. Sliders that may be assembled with the zipper by a transverse movement, while they may be of the flexible plastic one-piece type as disclosed in Laguere U.S. Pat. No. 3,426,396, preferably are of the foldable plastic type, examples of which are disclosed in Herrington et al U.S. Pat. No. 5,010,627, Herrington et al U.S. Pat. No. 5,063,644 and Herrington et al U.S. Pat. No. 5,067,208 and Herrington U.S. Pat. No. 5,070,583. While sliders have heretofore been assembled endwise with zippers, this method of assembly does not lend itself to a continuous bag making process. It would be desirable to utilize an endwise assembly of a slider on a zipper in a continuous bag making process and thus permit the use of a relatively strong plastic one-piece slider which is structurally stronger than one that has to be assembled transversely on the bag line.